Water-barrier performance of an encapsulating film

ABSTRACT

A method and apparatus for depositing a material layer onto a substrate is described. The method includes delivering a mixture of precursors for the material layer into a process chamber and depositing the material layer on the substrate at low temperature. The material layer can be used as an encapsulating layer for various display applications which require low temperature deposition process due to thermal instability of underlying materials used. In one aspect, the encapsulating layer includes one or more material layers (multilayer) having one or more barrier layer materials and one or more low-dielectric constant materials. The encapsulating layer thus deposited provides reduced surface roughness, improved water-barrier performance, reduce thermal stress, good step coverage, and can be applied to many substrate types and many substrate sizes. Accordingly, the encapsulating layer thus deposited provides good device lifetime for various display devices, such as OLED devices. In another aspect, a method of depositing an amorphous carbon material on a substrate at low temperature is provided. The amorphous carbon material can be used to reduce thermal stress and prevent the deposited thin film from peeling off the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 11/133,130 (APPM/008838.P1), titled “Improving Water-BarrierPerformance of an Encapsulating Film”, filed May 18, 2005, whichapplication is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 10/876,440, (APPM/008838), titled “Method toimprove water-barrier performance by changing film surface morphology”,filed Jun. 25, 2004. The aforementioned related patent applications areherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to the depositionof thin films using chemical vapor deposition processing. Moreparticularly, this invention relates to a process for depositing thinfilms onto large area substrates.

2. Description of the Related Art

Organic light emitting diode (OLED) displays have gained significantinterest recently in display applications in view of their fasterresponse times, larger viewing angles, higher contrast, lighter weight,lower power and amenability to flexible substrates, as compared toliquid crystal displays (LCD). After efficient electroluminescence (EL)was reported by C. W. Tang and S. A. Van Slyke in 1987, practicalapplication of OLED is enabled by using two layers of organic materialssandwiched between two electrodes for emitting light. The two organiclayers, in contrast to the old single organic layer, include one layercapable of monopolar (hole) transport and the other layer forelectroluminescence and thus lower the required operating voltage forOLED display.

In addition to organic materials used in OLED, many polymer materialsare also developed for small molecule, flexible organic light emittingdiode (FOLED) and polymer light emitting diode (PLED) displays. Many ofthese organic and polymer materials are flexible for the fabrication ofcomplex, multi-layer devices on a range of substrates, making them idealfor various transparent multi-color display applications, such as thinflat panel display (FPD), electrically pumped organic laser, and organicoptical amplifier.

Over the years, layers in display devices have evolved into multiplelayers with each layer serving different function. FIG. 1 shows anexample of an OLED device structure built on a substrate 101. After atransparent anode layer 102, such as an indium tin oxide (ITO) layer, isdeposited on the substrate 101, a stack of organic layers are depositedon the anode layer 102. The organic layers could comprise ahole-injection layer 103, a hole-transport layer 104, an emissive layer105, an electron-transport layer 106 and an electron injection layer107. It should be noted that not all five layers of organic layers areneeded to build an OLED cell. For example, in some cases, only ahole-transport layer 104 and an emissive layer 105 are needed. Followingthe organic layer deposition, a metallic cathode 108 is deposited on topof the stack of organic layers. When an appropriate voltage 110(typically a few volts) is applied to the cell, the injected positiveand negative charges recombine in the emissive layer to produce light120 (electroluminescence). The structure of the organic layers and thechoice of anode and cathode are designed to maximize the recombinationprocess in the emissive layer, thus maximizing the light output from theOLED devices.

The lifetime of display devices can be limited, characterized by adecrease in EL efficiency and an increase in drive voltage, due to thedegradation of organic or polymer materials, the formation ofnon-emissive dark spots, and crystallization of the organic layers athigh temperature of about 55° C. or higher, e.g., crystallization of thehole transport materials can occur at room temperature. Therefore, a lowtemperature deposition process for these materials, such as at about100° C. or lower is needed. In addition, the main reason for thematerial degradation and dark spot problems is moisture and oxygeningress. For example, exposure to humid atmospheres is found to inducethe formation of crystalline structures of 8-hydroxyquinoline aluminum(Alq₃), which is often used as the emissive layer, resulting in cathodedelamination, and hence, creating non-emissive dark spots growing largerin time. In addition, exposure to air or oxygen may cause cathodeoxidation and once organic material reacts with water or oxygen, theorganic material is dead.

Currently, most display manufacturers use metal-can or glass-canmaterials as an encapsulation layer to protect organic materials in thedevice from water (H₂O) or oxygen (O₂) attack. FIG. 2 illustrates theconventional packaging of an OLED device 200 on a substrate 201 withglass or metal encapsulating materials 205. The device 200 includes ananode layer 202 and a cathode layer 204 with multiple layers of organicmaterials 203. The metal or glass materials 205 are attached to thesubstrate 201 like a lid using a bead of UV-cured epoxy 206. However,moisture can easily penetrate through the epoxy 206 and damage thedevice 200.

Other materials, such as inorganic materials, e.g., silicon nitride(SiN), silicon oxynitride (SiON) and silicon oxide (SiO), prepared byplasma enhanced chemical vapor deposition (PECVD), can also be used asan effective encapsulation/barrier layer against moisture, air andcorrosive ions for such devices. However, it is very difficult togenerate water-barrier inorganic encapsulation materials using a lowtemperature deposition process because the resulting film is less denseand has high defect pinhole structures. It is important to note that thepresence of residual moisture in the organic layers may also promote theAlq₃ crystallization process even in encapsulated devices. In addition,oxygen and humidity being trapped during encapsulation and infiltratinginto the OLED device to be in contact with the cathode and organicmaterials generally result in dark spot formation, which is a frequentOLED destroying defect. Therefore, a good encapsulation/barrier filmalso requires low water vapor transmission rate (WVTR).

Additional problems with thin film inorganic silicon nitride (SiN)related materials as the encapsulation/barrier layer arise. If theencapsulating layer is thick to serve as a good oxygen and waterbarrier, it is usually hard, fragile, and too thick to adhere well to asubstrate surface, resulting in cracking or peeling off the substratesurface, especially at high temperature and humidity stressedconditions. If the encapsulating layer is made thin to improve adhesionand thermal stability, it is not thick enough as a moisture barrier.Therefore, additional layers or other manipulation may be required.

Thus, there is still a need for methods of depositing low temperatureencapsulation/barrier films onto large area substrates with improvedwater-barrier and thermal stress performance to protect the devicesunderneath.

SUMMARY OF THE INVENTION

Embodiments of the invention generally provide a method and apparatusfor depositing an encapsulating film onto a substrate. In oneembodiment, a method for forming a multilayer encapsulating film onto asubstrate placed in a substrate processing system includes depositingone or more silicon-containing inorganic barrier layers onto the surfaceof the substrate at a substrate temperature of about 200° C. or lower,and depositing one or more low-dielectric constant material layersalternating with the one or more silicon-containing inorganic barrierlayers. The one or more silicon-containing inorganic barrier layers aredeposited by delivering a first mixture of precursors and a hydrogen gasinto the substrate processing system to improve water-barrierperformance of the encapsulating layer. The one or more low-dielectricconstant material layers are deposited by delivering a second mixture ofprecursors into the substrate processing system.

In another embodiment, a method of forming a multilayer encapsulatingfilm onto a substrate placed in a substrate processing system, includesdepositing a plurality of silicon-containing inorganic barrier layersonto the surface of the substrate by delivering a silicon-containingcompound into the substrate processing system, and depositing one ormore low-dielectric constant material layers in between the one or moresilicon-containing inorganic barrier layers at a substrate temperatureof about 200° C. or lower by delivering a carbon-containing compound anda hydrogen gas into the substrate processing system. Accordingly, themultilayer encapsulating film having the plurality of silicon-containinginorganic barrier layers and the one or more low-dielectric constantmaterial layers is generated on the surface of the substrate.

In yet another embodiment, a method for depositing a low-dielectricconstant material layer onto a substrate at low temperature is provided.The method includes placing the substrate in a process chamber,generating a plasma inside the process chamber, depositing thelow-dielectric constant material layer onto the substrate at a substratetemperature of about 200° C. or lower from a mixture of acarbon-containing compound and a hydrogen gas into the process chamber.Accordingly, the film uniformity of the deposited low-dielectricconstant material layer is improved to about +/−10% or less.

In still another embodiment, a method for depositing an encapsulatinglayer, having one or more layers of silicon-containing inorganic barriermaterials and low-dielectric constant materials, onto a substrate isprovided. The method includes delivering a first mixture of precursorsfor a silicon-containing inorganic barrier layer into the substrateprocessing system and delivering a hydrogen gas into the substrateprocessing system, and controlling the temperature of the substrate to atemperature of about 150° C. or lower and generating a plasma to depositthe silicon-containing inorganic barrier layer on the surface of thesubstrate. The method further includes delivering a second mixture ofprecursors for a low-dielectric constant material layer into thesubstrate processing system and delivering a hydrogen gas into thesubstrate processing system, and controlling the temperature of thesubstrate to a temperature of about 150° C. or lower and generating aplasma to deposit the low-dielectric constant material layer onto thesurface of the silicon-containing inorganic barrier layer. The methodfurther includes depositing the encapsulating layer onto the substrateby repeating the above mentioned steps until a thickness of theencapsulating layer of about 15,000 angstroms or more is obtained.

In still another embodiment, an apparatus to deposit a low temperaturematerial layer onto a substrate is also provided. The apparatusincludes, a substrate support disposed in a process chamber to support asubstrate, such as a large area substrate, a RF source coupled to theprocess chamber to provide a plasma inside the process chamber, asilicon-containing compound supply source coupled to the processchamber, a hydrogen gas supply source coupled to the process chamber, acarbon-containing compound supply source coupled to the process chamber,and a controller coupled to the process chamber to control thetemperature of the substrate to about 200° C. or lower during substrateprocessing and adapted to deposit an encapsulating layer having one ormore low-dielectric constant material layers in between one or moresilicon-containing inorganic barrier layers.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 depicts a cross-sectional schematic view of an OLED device.

FIG. 2 depicts a cross-sectional schematic view of an OLED device withan encapsulating material (glass or metal) attached on top.

FIG. 3 depicts a cross-sectional schematic view of an OLED device withan encapsulating layer deposited on top in accordance with oneembodiment of the invention.

FIG. 4 is a schematic cross-sectional view of one embodiment of aprocess chamber in accordance with the invention.

FIG. 5 depicts a cross-sectional schematic view of one embodiment of anencapsulating layer deposited in accordance with one method of theinvention.

FIG. 6 is a flow chart of one method of forming a multilayerencapsulating film on a substrate inside a substrate processing systemin accordance with embodiments of the invention.

FIG. 7 is a flow chart of one method of depositing a low-dielectricconstant material on a substrate inside a process chamber in accordancewith embodiments of the invention.

FIG. 8 is a flow chart of another method of forming a multilayerencapsulating film on a substrate inside a substrate processing systemin accordance with embodiments of the invention

FIG. 9 illustrates optical properties of one exemplary barrier layer andexemplary low-dielectric constant material layer deposited by the methodof the invention.

FIG. 10 illustrates one exemplary multilayer encapsulating film havingfour layers of silicon nitride inorganic barrier films and three layersof amorphous carbon low-dielectric constant films deposited by onemethod of the invention.

DETAILED DESCRIPTION

The present invention generally relates to a method of improvingwater-barrier and thermal stability performance between a substrate anda film/layer deposited thereon. The invention describes using a hydrogengas to reduce film surface roughness, resulting in a smooth filmsurface. Accordingly, high level of uniformity of a film deposited on asubstrate surface can be obtained. The smooth surface of the depositedfilm further prevents water and oxygen penetrating from atmosphere intothe film and shows much lower WVTR (Water Vapor Transmission Rate)value. WVTR is a key parameter to indicate water-barrier performance inthe Flat Panel Display (FPD) industry. Further, the invention provides amethod and apparatus to deposit an encapsulating/barrier layer on thesurface of a substrate, such as a display device, to greatlyenhance/lengthen the lifetime of the device.

In addition, the invention describes a method of depositing alow-dielectric constant material layer at a low temperature, such asabout 200° C. or lower, onto a large area substrate surface. Thelow-dielectric constant material layer can be an amorphous carbonmaterial, a diamond-like-carbon material, carbon-doped siliconcontaining material, among others. The low-dielectric constant materialand/or amorphous carbon material can be used as portions of anencapsulating layer to improve film uniformity, film adhesion, andthermal stability of the encapsulating layer. Accordingly, one or morelayers of low-dielectric constant materials or amorphous carbonmaterials can be deposited on a substrate surface to function asadhesion enhancing layers or thermal stress relaxation layers to improvewater performance of display devices, such as OLED devices, amongothers.

The invention further provides a single-layer or multilayerencapsulating film that can be used to prevent water and oxygen fromdiffusing onto a surface of substrate. The single-layer encapsulatingfilm may be a silicon-containing inorganic barrier material, such assilicon nitride, silicon oxynitride, silicon oxide, silicon carbide,among others. The multilayer encapsulating film may include one or morebarrier layers and one or more low-dielectric constant material layers.The one or more low-dielectric constant material layers are functionedto enhance adhesion and thermal stability of the encapsulating layerand/or the one or more barrier layers.

In one embodiment, the one or more low-dielectric constant materiallayers are deposited in between the one or more barrier layers. Forexample, alternating layers of at least one low-dielectric constantmaterial layer and at least one barrier layer are deposited on a surfaceof a substrate, such as a display device.

In another embodiment, a first barrier layer is deposited onto a surfaceof a substrate to provide good water-barrier performance before a firstlow-dielectric constant material layer. In still another embodiment, amultilayer encapsulating film is deposited on top of a substrate surfacesuch that a final layer of a silicon-containing inorganic barriermaterial is deposited to provide good water-barrier performance of themultilayer encapsulating film.

Substrates of the invention can be circular or polygonal forsemiconductor wafer manufacturing and flat panel display manufacturing.The surface area of a rectangular substrate for flat panel display istypically large, for example, a rectangle of about 500 mm² or larger,such as at least about 300 mm by about 400 mm, e.g., about 120,000 mm²or larger. In addition, the invention applies to any devices, such asOLED, FOLED, PLED, organic TFT, active matrix, passive matrix, topemission device, bottom emission device, solar cell, etc., and can be onany of the silicon wafers, glass substrates, metal substrates, plasticfilms (e.g., polyethylene terephthalate (PET), polyethylene naphthalate(PEN), etc.), plastic epoxy films, among others.

FIG. 3 shows an exemplary embodiment of an encapsulating layer 305deposited on a substrate 301 of a display device 300 using methods ofthe invention. For example, a transparent anode layer 302 is depositedon the substrate 301, which could be made of glass or plastic, such aspolyethyleneterephthalate (PET) or polyethyleneterephthalate (PEN). Anexample of the transparent anode layer 302 is an indium-tin-oxide (ITO)with the thickness in the range of about 200 Å to about 2000 Å.

Multiple layers of organic or polymer materials 303 can be deposited ontop of the anode layer 302. For example, a material layer 303 caninclude a hole-transport layer deposited on top of the anode layer.Examples of the hole-transport layer include: diamine, such as anaphthyl-substituted benzidine (NPB) derivative, orN,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine(TPD), for a thickness of about 200 Å to about 1000 Å. Following thehole-transport layer deposition, an emissive layer can be deposited.Materials for the emissive layer typically belong to a class offluorescent metal chelated complexes. An example is 8-hydroxyquinolinealuminum (Alq₃). The thickness of the emissive layer is typically in therange of about 200 Å to about 1500 Å. After the emissive layer isdeposited, these organic layers are patterned. OLED displays aretypically deposited on a pre-patterned surface of the substrate byink-jet printing or evaporation method. After patterning of the organicmaterials 303, a top electrode layer 304, such as a cathode layer, isthen deposited and patterned. The top electrode layer 304 can be ametal, a mixture of metals or an alloy of metals. An example of the topelectrode material is an alloy of magnesium (Mg), silver (Ag) andaluminum (Al) in the thickness range of about 1000 Å to about 3000 Å.

The encapsulating layer 305 is deposited on top of the substrate surfaceafter construction of the display device 300, such as an OLED device, iscomplete. Exemplary materials of the encapsulating layer 305 of theinvention include a thin layer of inorganic nitride film, inorganicoxide film, and polymer-type organic film deposited in the thicknessrange of about 500 Å to about 500,000 Å, such as between about 2,000 Åto about 50,000 Å. For example, silicon nitride (SiN), siliconoxynitride (SiON), silicon oxide (SiO), and silicon carbide (SiC), amongothers, can be used as the encapsulating material.

One embodiment of the invention provides that the encapsulating layer305 deposited on a substrate 301 includes one or more layers ofbarrier/encapsulating materials, such as inorganic nitride, inorganicoxide film and polymer-type organic material. In addition, the inventionfurther provides using one or more additional material layers, such asvarious carbon-containing materials and polymer-type organic materials,and low-dielectric constant materials, e.g., amorphous carbon,diamond-like-carbon, carbon-doped silicon containing material, etc., inthe encapsulating layer 305 to enhance adhesion and soften theencapsulating layer 305.

Substrate Processing System

The invention is illustratively described below in reference to a plasmaenhanced chemical vapor deposition system configured to process largearea substrates, such as various parallel-plate radio-frequency (RF)plasma enhanced chemical vapor deposition (PECVD) systems including AKT™1600, AKT™ 3500, AKT™ 4300, AKT™ 5500, AKT™ 10K, AKT™ 15K, and AKT™ 25Kfor various substrate sizes, available from AKT™, a division of AppliedMaterials, Inc., Santa Clara, Calif. However, it should be understoodthat the invention has utility in other system configurations, such asother chemical vapor deposition systems and any other film depositionsystems, including those systems configured to process round substrates.

The invention provides a substrate processing system having one or moreprocess chambers in order to deposit a single-layer or multilayerencapsulating film on a substrate surface. The multilayer encapsulatingfilm of the invention can be deposited in the same or differentsubstrate processing system, in the same or different process chambersof a substrate processing system. In one embodiment, the multilayerencapsulating film is deposited in the same vacuum substrate processingsystem to save time and improve processing throughput. In anotherembodiment, the multilayer encapsulating film of the invention can bedeposited on a substrate surface in the same or different processchambers inside a multi-chambered substrate processing system. Forexample, the multilayer encapsulating film having one or moresilicon-containing inorganic barrier layers and one or morelow-dielectric constant material layers can be efficiently deposited ina chemical vapor deposition (CVD) system without taking the substrateout of the CVD system and decrease the possibility of water and oxygento diffuse onto the substrate surface.

FIG. 4 is a schematic cross-sectional view of one embodiment of asubstrate processing system 400 having one or more plasma enhancedchemical vapor deposition chambers, available from AKT™, a division ofApplied Materials, Inc., Santa Clara, Calif. The substrate processingsystem 400 generally includes one or more processing chambers 402,substrate input/output chambers, a main transfer robot for transferringsubstrate among the substrate input/output chambers and the processingchambers 402, and a mainframe controller for automatic substrateprocessing control.

The processing chamber 402 is usually coupled to one or more supplysources 404 for delivery one or more source compounds and/or precursors.The one or more supply sources 404 may include a silicon-containingcompound supply source, a hydrogen gas supply source, acarbon-containing compound supply source, among others. The processingchamber 402 has walls 406 and a bottom 408 that partially define aprocess volume 412. The process volume 412 is typically accessed througha port and a valve (not shown) to facilitate movement of a substrate440, such as a large area glass substrate, into and out of theprocessing chamber 402. The walls 406 support a lid assembly 410 thatcontains a pumping plenum 414 that couples the process volume 412 to anexhaust port (that includes various pumping components, not shown) forexhausting any gases and process by-products out of the processingchamber 402.

A temperature controlled substrate support assembly 438 is centrallydisposed within the processing chamber 402. The substrate supportassembly 438 supports the substrate 440 during processing. The substratesupport assembly 438 comprises an aluminum body 424 that encapsulates atleast one embedded heater 432. The heater 432, such as a resistiveelement, disposed in the substrate support assembly 438, is coupled toan optional power source 474 and controllably heats the support assembly438 and the substrate 440 positioned thereon to a predeterminedtemperature.

In one embodiment, the temperature of the heater 432 can be set at about200° C. or lower, such as 150° C. or lower, or between about 20° C. toabout 100° C., depending on the deposition/processing parameters for amaterial layer being deposited. For example, the heater can be set atbetween about 60° C. to about 80° C., such as at about 70° C., for a lowtemperature deposition process.

In another embodiment, a port having hot water flowing therein isdisposed in the substrate support assembly 438 to maintain the substrate440 at a uniform temperature of 200° C. or lower, such as between about20° C. to about 100° C. Alternatively, the heater 432 can be turned offwith only hot water flowing inside the substrate support assembly 438 tocontrol the temperature of the substrate during deposition, resulting ina substrate temperature of about 100° C. or lower for a low temperaturedeposition process.

The support assembly 438 generally is grounded such that RF powersupplied by a power source 422 to a gas distribution plate assembly 418positioned between the lid assembly 410 and substrate support assembly438 (or other electrode positioned within or near the lid assembly ofthe chamber) may excite gases present in the process volume 412 betweenthe support assembly 438 and the gas distribution plate assembly 418.The RF power from the power source 422 is generally selectedcommensurate with the size of the substrate to drive the chemical vapordeposition process.

In one embodiment, a RF power of about 10 W or larger, such as betweenabout 400 W to about 5000 W, is applied to the power source 422 togenerate an electric field in the process volume 412. For example, apower density of about 0.2 watts/cm² or larger, such as between about0.2 watts/cm² to about 0.8 watt/cm², or about 0.45 watts/cm², can beused to be compatible with a low temperature substrate deposition methodof the invention. The power source 422 and matching network (not shown)create and sustain a plasma of the process gases from the precursorgases in the process volume 412. Preferably high frequency RF power of13.56 MHz can be used, but this is not critical and lower frequenciescan also be used. Further, the walls of the chamber can be protected bycovering with a ceramic material or anodized aluminum material.

Generally, the support assembly 438 has a lower side 426 and an upperside 434, supporting the substrate 440. The lower side 426 has a stem442 coupled thereto and connected to a lift system (not shown) formoving the support assembly 438 between an elevated processing position(as shown) and a lowered substrate transfer position. The stem 442additionally provides a conduit for electrical and thermocouple leadsbetween the support assembly 438 and other components of the system 400.A bellows 446 is coupled to the substrate support assembly 438 toprovide a vacuum seal between the process volume 412 and the atmosphereoutside the processing chamber 402 and facilitate vertical movement ofthe support assembly 438.

In one embodiment, the lift system is adjusted such that a spacingbetween the substrate and the gas distribution plate assembly 418 isabout 400 mils or larger, such as between about 400 mils to about 1600mils, e.g., about 900 mils, during processing. The ability to adjust thespacing enables the process to be optimized over a wide range ofdeposition conditions, while maintaining the required film uniformityover the area of a large substrate. The combination of a groundedsubstrate support assembly, a ceramic liner, high pressures and closespacing gives a high degree of plasma confinement between the gasdistribution plate assembly 418 and the substrate support assembly 438,thereby increasing the concentration of reactive species and thedeposition rate of the subject thin films.

The support assembly 438 additionally supports a circumscribing shadowframe 448. Generally, the shadow frame 448 prevents deposition at theedge of the substrate 440 and support assembly 438 so that the substratedoes not stick to the support assembly 438. The lid assembly 410typically includes an entry port 480 through which process gasesprovided by the gas source 404 are introduced into the processingchamber 402. The entry port 480 is also coupled to a cleaning source482. The cleaning source 482 typically provides a cleaning agent, suchas disassociated fluorine, that is introduced into the processingchamber 402 to remove deposition by-products and films from processingchamber hardware, including the gas distribution plate assembly 418.

The gas distribution plate assembly 418 is typically configured tosubstantially follow the profile of the substrate 440, for example,polygonal for large area substrates and circular for wafers. The gasdistribution plate assembly 418 includes a perforated area 416 throughwhich precursors and other gases, such as hydrogen gas, supplied fromthe gas source 404 are delivered to the process volume 412. Theperforated area 416 is configured to provide uniform distribution ofgases passing through the gas distribution plate assembly 418 into theprocessing chamber 402. The gas distribution plate assembly 418typically includes a diffuser plate 458 suspended from a hanger plate460. A plurality of gas passages 462 are formed through the diffuserplate 458 to allow a predetermined distribution of gas passing throughthe gas distribution plate assembly 418 and into the process volume 412.

Gas distribution plates that may be adapted to benefit from theinvention are described in commonly assigned U.S. patent applicationSer. No. 09/922,219, filed Aug. 8, 2001 by Keller et al. and issued asU.S. Pat. No. 6,772,827; Ser. No. 10/140,324, filed May 6, 2002 andissued as U.S. Pat. No. 7,008,484; and Ser. No. 10/337,483, filed Jan.7, 2003 by Blonigan et al. and published as United States PatentPublication No. 2004/0129211 A1; U.S. Pat. No. 6,477,980, issued Nov.12, 2002 to White et al.; and U.S. patent application Ser. No.10/417,592, filed Apr. 16, 2003 by Choi et al. and issued as U.S. Pat.No. 6,942,753, which are hereby incorporated by reference in theirentireties. Although the invention has been described in accordance withcertain embodiments and examples, the invention is not meant to belimited thereto. The CVD process herein can be carried out using otherCVD chambers, adjusting the gas flow rates, pressure, plasma density,and temperature so as to obtain high quality films at practicaldeposition rates.

Deposition of an Encapsulating Film

FIG. 5 shows an exemplary display device 500 fabricated using methods ofthe invention according to embodiments of the invention. The displaydevice 500 may include a substrate 501 and a device 502, which may beany type of display devices which need to be encapsulated. For example,the device 502 can be OLED, FOLED, PLED, organic TFT, solar cell, topemissive device, bottom emissive device, among others. An encapsulatinglayer having a thickness of about 1,000 Å or larger is then depositedusing methods of the invention to prevent water/moisture and air topenetrate into the substrate 501 and the device 502.

In one embodiment, a multilayer encapsulating film having at least onebarrier layer and at least one low-dielectric constant material layer isdeposited on top of the device 502 to prevent water and other gases orliquids from diffusing into the device 502 and short-circuit the device502 without the multilayer encapsulating film being cracked or fallenoff the surface of the device 502 due to poor adhesion and thermalinstability. As shown in FIG. 5, the multilayer encapsulating filmincludes alternating layers of one or more barrier layers 511, 512, 513,etc., and one or more low-dielectric constant material layers 521, 522,etc.

In one aspect, the invention provides the one or more low-dielectricconstant material layers 521, 522 deposited in between the one or morebarrier layers 511, 512, 513. In another aspect, the final layer of themultilayer encapsulating film deposited on top of a substrate surface isa barrier layer, such as the barrier layer 513. The final layer includesa barrier material, such as silicon nitride, silicon oxynitride, siliconoxide, and silicon carbide, among others, deposited using method of theinvention to serve as a good water and oxygen barrier for the finalsurface of the exemplary display device 500.

The first layer on top of the device 502 can be a low-dielectricconstant material layer or a barrier layer. In a preferred embodiment,the invention provides a first layer deposited on top of the device 502being a barrier layer to enhance water-barrier performance for theexemplary display device 500. For example, a first barrier layer, suchas the barrier layer 511, can be deposited before an adhesion enhancinglayer and/or a low-dielectric constant material layer, such as thelow-dielectric constant material layer 521. Accordingly, thelow-dielectric constant material layers are deposited on top of thebarrier layers to promote adhesion between adjacent barrier layers suchthat the multilayer encapsulating film can be deposited into sufficientthickness, such as about 8,000 Å or larger.

FIG. 6 illustrates a flow chart of a deposition method 600 in accordancewith one embodiment of the invention. First of all, a substrate isplaced in a process chamber of a substrate processing system fordepositing a material layer, such as an encapsulating layer 305, on thesubstrate. The method 600 optionally includes a step of forming a deviceon the substrate. Exemplary devices include, but is not limited to,OLED, PLED, and FOLED, among others.

At step 602, a first mixture of precursors for a barrier layer, such asa silicon-containing barrier layer, is delivered into the substrateprocessing system. The first mixture of precursors may include one ormore silicon-containing gases, such as silane (SiH₄), SiF₄, and Si₂H₆,among others. The first mixture of precursors may further include one ormore nitrogen-containing gases, such as ammonia (NH₃), nitrous oxide(N₂O), nitric oxide (NO), and nitrogen gas (N₂), among others. The firstmixture of precursors may also include a carbon-containing gas and/or anoxygen-containing gas.

For example, a silicon nitride barrier layer can be deposited from amixture of a silicon-containing gas and a nitrogen-containing gas, suchas a mixture of silane, ammonia, and/or nitrogen gas. As anotherexample, a silicon oxynitride barrier layer can be deposited from amixture of a silicon-containing gas, an oxygen-containing gas, and anitrogen-containing gas, such as a mixture of silane, nitrous oxide,and/or nitrogen gas.

At step 604, a hydrogen gas is delivered into the substrate processingsystem and a silicon-containing inorganic barrier layer is depositedonto the surface of a substrate at a substrate temperature of about 200°C. or lower at step 606. The substrate temperature during substrateprocessing for a display device, such as an OLED device 300, needs to bekept at low temperature due to thermal instability of organic layers inthe OLED device, such as the multiple layers of organic materials 303.In generally, a temperature of about 150° C. or lower is desired, suchas about 100° C. or lower, about 80° C. or lower, or between about 20°C. and about 80° C.

It is found that the presence of a hydrogen gas reduces the surfaceroughness of the deposited silicon-containing inorganic barrier layer,resulting in a surface roughness measurement (RMS) of from about 40 Å toabout 70 Å being reduced to about 40 Å or lower, such as about 15 Å orlower, preferably about 10 Å or lower. We have also found that a barrierlayer with reduced surface roughness (a smooth surface) significantlyprevents water penetration into the barrier layer, making it a goodencapsulating layer for any materials underneath (e.g., organic and/orpolymer materials used for display devices). The introduction ofhydrogen gas prevents water penetration with a water vapor transmissionrate of less than about 1×10⁻² grams per square meter per day, such asbetween about 1×10⁻³ grams per square meter per day to about 1×10⁻⁴grams per square meter per day as measured at about 38° C. with 90%relative humidity.

At step 608, a second mixture of precursors for a low-dielectricconstant material layer is delivered into the same or a differentsubstrate processing system. Preferably, the low-dielectric constantmaterial layer is processed in the same substrate processing system asthe barrier layer deposition system for increasing the throughput ofsubstrate processing. In addition, the substrate can be placed in thesame or different process chamber of a substrate processing system fordepositing the barrier layer and/or the low-dielectric constant materialfor ease of operation and reducing the chance of air and moistureexposure when taking the substrate in and out of a substrate processingsystem.

The second mixture of precursors may include one or morecarbon-containing compounds, such as acetylene (C₂H₂), ethane (C₂H₆),ethene (C₂H₄), methane (CH₄), propylene (C₃H₆), propyne (C₃H₄), propane(C₃H₈), butane (C₄H₁₀), butylene (C₄H₈), butadiene (C₄H₆), benzene(C₆H₆), and toluene (C₇H₈), among others.

The low-dielectric constant material layer may be an amorphous carbonmaterial, a diamond-like-carbon material, and carbon-doped siliconcontaining material, among others. For example, an amorphous carbonlayer can be deposited from a mixture of a carbon-containing compound,such as acetylene (C₂H₂).

At step 610, a hydrogen gas is delivered into the substrate processingsystem and a low-dielectric constant material layer is deposited ontothe surface of a substrate at a substrate temperature of about 200° C.or lower at step 612. Preferably, a substrate temperature of about 150°C. or lower, such as about 100° C. or lower, about 80° C. or lower, orbetween about 20° C. and about 80° C., is used.

It is found that the presence of a hydrogen gas improves film uniformityof the deposited low-dielectric constant material layer, resulting in afilm uniformity measurement of from between about +/−15% to about +/−35%being improved to about +/−10% or lower, such as about +/−5% or lower orabout +/−3% or lower. We have also found that a low-dielectric constantmaterial layer with improved film uniformity significantly improves thestep coverage of the deposited low-dielectric constant material layer,such that additional multilayer can be deposited with good stepcoverage. For example, a step coverage of about 80% or higher, e.g.,about 95% or higher, for layers of the encapsulating film is observed.

At step 614, if a predetermined thickness of an encapsulating filmhaving the silicon-containing inorganic barrier layer and thelow-dielectric constant material layer is obtained, the depositionprocess can be ended at step 616. However, if a predetermined thicknessof the encapsulating layer is not obtained, then any of the combinationsof steps 602, 604, 606, 608, 610, 612 can be repeated. For example, oncea desired thickness is obtained after one or more silicon-containinginorganic barrier layer and one or more low-dielectric constant materiallayers are deposited, the method 600 may end where a silicon-containinginorganic barrier layer or a low-dielectric constant material layers islast deposited.

The thickness of the encapsulating layer can vary. For example, athickness of about 1,000 Å or larger, e.g., about 10,000 Å or larger,such as between about 20,000 Å to about 60,000 Å, may be desired. Wehave found out that the thickness of an encapsulating film for thedevice 502 is correlated to its air and moisture barrier performance,thus lengthening the lifetime of the device 502. Using methods of theinvention, a lifetime of about 40 days or longer for the device 502,such as about 45 days or longer, or about 60 days or longer can beobtained.

In one aspect, a single barrier layer deposited using methods of theinvention can be used as an encapsulating film for a display device ofthe invention. For example, a single silicon nitride barrier layerhaving a thickness of about 10,000 Å can be used as an encapsulatingfilm. In another aspect, the invention provides a multilayerencapsulating film having at least one silicon-containing inorganicbarrier layer and at least one low-dielectric constant material layer.The silicon-containing inorganic barrier layer may have a thickness ofbetween about 1,000 Å to about 10,000 Å, such as between about 2,000 Åto about 8,000 Å. The low-dielectric constant material layer may have athickness of between about 1,000 Å to about 10,000 Å. It is found thatthe presence of a low-dielectric constant material increase adhesionbetween adjacent barrier layers with improved thermal stability, makingmultilayer of silicon-containing inorganic barrier layer at a sufficientthickness possible.

One exemplary encapsulating film of the invention may include twosilicon nitride layers and an amorphous carbon material layer in betweenthe silicon nitride layer for a total thickness of about between about3,000 Å to about 30,000 Å. Another exemplary encapsulating film of theinvention may include five silicon nitride layers and four amorphouscarbon material layers in between the five silicon nitride layers for atotal thickness from about 9,000 Å to about 90,000 Å.

The surface of the substrate may be cleaned with a plasma before orafter each layer is deposited. For example, one or more cleaning gasescan be supplied to the process chamber and an electric field from an RFpower source or microwave power source can be applied to generate acleaning plasma. The cleaning gases may include, but are not limited to,oxygen-containing gas (e.g., oxygen, carbon dioxide),hydrogen-containing gas (e.g., hydrogen gas), nitrogen-containing gas(e.g., ammonia, nitrous oxide), inert gas (e.g., helium, argon), amongothers. Examples of hydrogen-containing gas include, but are not limitedto, hydrogen gas (H₂) and ammonia (NH₃), among others. In addition, whenthe chamber is cleaned by a plasma generated from a cleaning gas, thecleaning gas may optionally be delivered with a carrier gas and suppliedinto the chamber. Exemplary carrier gas includes inert gases, such ashelium and argon, among others. For example, an in-situ oxygen plasmamay be generated to clean away any material inside the process chamber,such as materials on the chamber walls, gas distribution plate,everywhere, after previous substrate processing and substrate removal.

It is noted that embodiments of the invention do not require the stepsto be performed in the order as described herein. For example, ahydrogen gas can be delivered into the process chamber before a mixtureof the precursors is delivered into the chamber, and in some cases,steps 602 and 604 can be performed at the same time. Similarly, steps608 and 610 can be performed at the same time.

Deposition of at Least One Silicon-Containing Barrier Layer

One or more silicon-containing inorganic barrier layers are depositedfrom a mixture of precursors delivered into the process chamber. Theprecursors may include a silicon-containing precursor, such as silane(SiH₄), Si₂H₆, SiF₄, among others, for depositing a layer of siliconnitride (SiN), silicon oxynitride (SiON) or silicon oxide (SiO), siliconcarbide (SiC), among others, as an encapsulating layer onto thesubstrate. The silicon-containing precursor can be delivered, forexample, at a flow rate of 10 sccm or larger, such as from about 100sccm to about 500 sccm for a substrate size of about 400 mm×about 500mm. A nitrogen-containing precursor can be delivered at a flow rate ofabout 5 sccm or larger, such as from about 100 sccm to about 6000 sccmfor various nitrogen-containing precursors.

For example, a mixture of the precursors may include silane, nitrousoxide, and nitrogen, among others, for depositing a silicon oxynitridefilm. Alternatively, silane, ammonia, and nitrogen, among others areused for depositing a silicon nitride film. Also, the precursors mayinclude silane, and nitrous oxide for depositing a silicon oxide film.In addition, each precursor can be delivered at different or the sameflow rate, depending on various deposition parameters required. It isunderstood that embodiments of the invention include scaling up orscaling down any of the process parameter/variables as described hereinaccording to substrate sizes, chamber conditions, etc., among others.

During deposition of the one or more silicon-containing inorganicbarrier layers, a hydrogen gas is delivered into the process chamber toimprove water-barrier performance of the encapsulating layer of theinvention. In addition, the introduction of the hydrogen gas is found toreduce surface roughness of the one or more silicon-containing inorganicbarrier layers, making it a good encapsulating layer.

The one or more silicon-containing inorganic barrier layers aredeposited onto the substrate by applying an electric field andgenerating a plasma inside the process chamber. The electric field canbe generated by applying a power source, such as radio-frequency power,microwave frequency power, to the process chamber. The power source canbe coupled to the process chamber inductively or capacitively. Inaddition, the pressure of the process chamber is maintained at about 0.5Torr to about 10 Torr.

As a result, the one or more silicon-containing inorganic barrier layersare deposited at a deposition rate of about 500 Å/min or larger, such asbetween about 1000 Å/min to about 3000 Å/min. The thickness of the oneor more silicon-containing inorganic barrier layers may be varied to arange of from about 1,000 Å to about 30,000 Å. Usually a thicker barrierlayer is better than a thinner barrier layer for preventing waterpenetration.

Conventional low temperature inorganic film deposition processes haveproduced undesired properties in an encapsulating layer. For example,the film is less dense and the surface of the film is rough with defectstructure and poor film property, such as high refractive index changeafter water test, high transmission fourier transform infrared spectra(FTIR) change, high water vapor transmission rate (WVTR) after watertest. As an example, deposition of a silicon nitride thin film with goodwater-barrier performance to be used as a good moisture barrier/filmwill be further illustrated herein below, but the invention is not meantto be limited to the details described herein.

Substrates (400 mm×500 mm in size) were brought under vacuum inside achamber of a conventional parallel-plate radio-frequency (RF) plasmaenhanced chemical vapor deposition (PECVD) system, AKT 1600 PECVD,available from Applied Materials, Inc., Santa Clara, Calif. with aspacing of about 900 mils. The temperature of the substrate support(susceptor) was set at about 60° C. for a low temperature depositionprocess. Mixtures of silane (SiH₄), ammonia (NH₃), nitrogen (N₂) in thepresence of hydrogen gas (H₂) were delivered into the chamber as thesource precursor gases for depositing a silicon nitride film as moistureand oxygen barrier. As a comparison, prior art methods of using silane(SiH₄), ammonia (NH₃), and a nitrogen (N₂) for depositing siliconnitride was prepared in parallel under the same process conditions. Thepressure inside the chamber is about 2.1 Torr. A plasma was sustainedwith RF power generator set at about 13.56 MHz and about 900 W.

Basic film properties were compared for films prepared from both processconditions. The results showed that silicon nitride films deposited inthe presence and absence of hydrogen source gas exhibit similar basicfilm properties initially with refractive index (RI) of about 1.7 toabout 1.9 and film stress of zero to about 2×10⁹ dynes/cm². Thedeposition rate is comparable for both films at about 1000 Å/min toabout 1500 Å/min. Thus, the presence of hydrogen gas does not affectbasic film properties or the deposition rate.

However, surface roughness after deposition (in the unit of root meansquare, RMS) for both films varied dramatically. Both films werecompared under microscope, and 3-dimensional surface roughness imageswere compared and surface roughness was measured. The average surfaceroughness for SiN film deposited without hydrogen source gas was about40 Å to about 70 Å, indicating a rough surface. The average surfaceroughness for SiN film deposited in the presence of hydrogen source gaswas about 9 Å to about 12 Å, indicating a smooth surface.

The comparison was more significant when both films were compared afterwater test to measure the effect of water/moisture on film property.According to Table 1 for a comparison of key water-barrier performance,it is found that H₂ source gas plays an important role to reduce filmsurface roughness into a smooth surface, and a smooth surface preventswater/oxygen penetration from atmosphere into the film inside, resultingin much lower WVTR (Water Vapor Transmission Rate) value, a keyparameter in the flat panel display industry to indicate resistance tomoisture/water. Water test to measure WVTR is a high-humidity testusually carried out by placing a test structure in a humidity chamberoperating at a temperature range of about 25° C. to about 100° C. andabout 40% to about 100% relative humidity (RH) for a specified amount oftime (in hours or days, etc.). The amount of water retained on thespecific size of the tested structure per test time was calculated togive a Water Vapor Transmission Rate (WVTR) at the tested temperatureand tested relative humidity. TABLE 1 Comparison of key water-barrierperformance SiN film without H₂ SiN film with H₂ Surface roughness afterabout 40 Å to about 70 Å about 9 Å to about deposition (RMS) 12 ÅRefractive Index (RI) 15% 0% change after water treatment (100° C./100hours) FTIR change after water O—H bond increased, No change treatment(100° C./100 Si—H bond reduced, hours) N—H bond reduced Water VaporTransmission More than about 1.0 × 10⁻² About 1.0 × 10⁻⁴ Rate (WVTR) at38° C./ g/m² day g/m² day to about 90% relative humidity 1.0 × 10⁻³ g/m²day

The transmission fourier transform infrared spectra (FTIR) before andafter water treatment for the SiN film deposited with hydrogen sourcegas were also performed and compared. Water treatment for comparison ofchange in FTIR and refractive index (RI) were also performed by soakingdifferent deposited films in hot water, such as about 100° C., for aspecified amount of time, e.g., about 100 hours. The FTIR spectra wererecorded in the range of 1500 cm⁻¹ to 4000 cm⁻¹. The Si—H, N—H, and O—Hbonds were indicated in the spectra. There is not much difference beforeand after water treatment, indicating no change of any bonds after watertreatment from the SiN film deposited with a hydrogen source gas. Theresults, as shown in Table 1, also indicated that, after treatment ofthe SiN film in water at about 100° C. for about 100 hours (hot andhumid), there is no change of refractive index for the SiN filmdeposited under the deposition conditions in the presence of hydrogengas as one of the precursor source gases. Together with the results oflow water vapor transmission rate (WVTR) measured after water test, allof which are indicative that a high quality silicon nitride wasdeposited with good water-barrier performance using a hydrogen gas aspart of source gas mixtures.

As a comparison, the transmission fourier transform infrared spectra(FTIR) change before and after water treatment for the SiN filmsdeposited using the prior art method without hydrogen source gas werealso performed and compared. The results demonstrated a big decrease inSi—H bond, a small decrease in N—H bond, and a small peak increase inO—H bond. The results, also shown in Table 1, indicated that, there isabout 15% change of refractive index for the SiN film deposited withouta hydrogen source gas. In addition, higher water vapor transmission rate(WVTR) was measured after water test. All of which are indicative thatthe silicon nitride film deposited in the absence of hydrogen source gasexhibits poor water-barrier performance.

Deposition of at Least One Low-Dielectric Constant Material Layer

Aspects of the invention provide alternatively depositing alow-dielectric constant material layer and a silicon-containinginorganic barrier layer. One exemplary low-dielectric constant materiallayer having a dielectric constant (K) of less than about 4 is anamorphous carbon material. Other examples of low-dielectric constantmaterials include carbon-containing low-dielectric constant materials,carbon-doped silicon material, diamond-like carbon material, amongothers.

FIG. 7 illustrates a flow chart of a deposition method 700 in accordancewith one embodiment of the invention. At step 702, a substrate is placedin a deposition process chamber for depositing a low-dielectric constantmaterial, such as an amorphous carbon material layer on the substrate.

At step 704, a mixture of precursors for the amorphous carbon materialis delivered into the process chamber. A wide variety of gas mixturesmay be used to deposit the low-dielectric constant material, andnon-limiting examples of such gas mixtures are provided below.Generally, the gas mixture may include one or more carbon-containingcompounds and/or hydrocarbon compounds. Suitable organiccarbon-containing compounds include aliphatic organic compounds, cyclicorganic compounds, or combinations thereof. Aliphatic organic compoundshave linear or branched structures comprising one or more carbon atoms.Organic carbon-containing compounds contain carbon atoms in organicgroups. Organic groups may include alkyl, alkenyl, alkynyl,cyclohexenyl, and aryl groups in addition to functional derivativesthereof. The carbon-containing precursor/compound can be delivered, forexample, at a flow rate of 10 sccm or larger, such as from about 100sccm to about 500 sccm for a substrate size of about 400 mm×about 500mm.

For example, the carbon-containing compound can have a formulaC_(x)H_(y), where x has a range of between 1 and 8 and y has a range ofbetween 2 and 18, including, but not limited to, acetylene (C₂H₂),ethane (C₂H₆), ethene (C₂H₄), propylene (C₃H₆), propyne (C₃H₄), propane(C₃H₈), methane (CH₄), butane (C₄H₁₀), butylene (C₄H₈), butadiene(C₄H₆), benzene (C₆H₆), toluene (C₇H₈), and combinations thereof.Alternatively, partially or completely fluorinated derivatives of thecarbon-containing compounds, for example, C₃F₈ or C₄F₈, may be used todeposit a fluorinated amorphous carbon layer, which may be described asan amorphous fluorocarbon layer. A combination of hydrocarbon compoundsand fluorinated derivatives of hydrocarbon compounds may be used todeposit the amorphous carbon layer or amorphous fluorocarbon layer.

A variety of gases may be added to the gas mixture to modify propertiesof the amorphous carbon material. An inert gas (e.g., helium, argon,neon, xenon, krypton, etc.), nitrogen (N₂), ammonia (NH₃), nitrous oxide(N₂O), nitric oxide (NO), or combinations thereof, among others,delivered at a flow rate of about 5 sccm or larger, such as betweenabout 100 sccm to about 6000 sccm, are used to control the density anddeposition rate of the low-dielectric constant amorphous carbon layer.Further, the addition of H₂ and/or NH₃ can be used to control thehydrogen ratio of the amorphous carbon layer to control layerproperties, such as reflectivity.

At step 706, a hydrogen gas is delivered into the process chamber toenhance film uniformity (decrease in % uniformity measurement). When thehydrogen gas is added as a source gas, a film uniformity of about +/−10%or lower, such as about +/−5% or lower or about +/−3% or lower, isobtained. In contrast, without adding the hydrogen gas, the depositedlow-dielectric constant amorphous carbon material is very rough andnon-uniform with a film uniformity measurement of between about +/−15%to about +/−35%. Without the hydrogen gas to improve film uniformity,there is a much more drastic impact on step coverage when multiplelayers are deposited. A low-dielectric constant amorphous carbonmaterial layer with enhanced film uniformity (a smooth and uniform filmsurface) significantly improves step coverage to about 80% or higher, oreven about 95% or higher, and also adheres well in betweensilicon-containing inorganic barrier layers in a multilayer film stack.

At step 708, an electric field is applied and a plasma is generatedinside the process chamber. The electric field can be generated byapplying a power source, such as radio-frequency power, microwavefrequency power, to the process chamber. The power source can be coupledto the process chamber inductively or capacitively. Power from a single13.56 MHz RF power source may be supplied to the process chamber to formthe plasma at a power density between about 0.14 watts/cm² and about 8.6Watts/cm², or a power level between about 100 watts and about 6000watts. A power density between about 0.25 watts/cm² and about 0.6watts/cm² is preferably supplied to the process chamber to generate theplasma. The RF power may be provided at a frequency between about 0.01MHz and 300 MHz. The RF power may be provided continuously or in shortduration cycles. RF power is coupled to the process chamber to increasedissociation of the compounds. The compounds may also be dissociated ina microwave chamber prior to entering the deposition chamber. However,it should be noted that the respective parameters may be modified toperform the plasma processes in various chambers and for differentsubstrate sizes.

The carbon-containing compound and the hydrogen gas are introduced tothe process chamber from a carbon-containing compound supply source anda hydrogen gas supply source through a gas distribution system and intothe process chamber. The gas distribution system is generally spacedbetween about 180 mils and about 2000 mils, such as about 900 mils, fromthe substrate on which the low-dielectric constant amorphous carbonlayer is being deposited upon. In addition, the pressure of the processchamber is maintained at about 100 milliTorr to about 20 Torr.

At step 710, the amorphous carbon material is deposited onto thesubstrate by applying the amorphous carbon layer at a substratetemperature of about 100° C. or lower, such as a substrate temperaturemaintained at between about −20° C. and about 100° C., and preferablymaintained at a temperature between about 20° C. and about 80° C. Apreferred amorphous carbon layer is deposited, in one embodiment, bysupplying acetylene to a plasma process chamber at a flow rate betweenabout 100 standard cubic centimeters per minute (sccm) and about 5,000sccm, such as about 200 sccm. A hydrogen gas is also added to theprocess chamber at a flow rate between about 100 sccm and about 2,500sccm, such as between about 200 sccm and about 600 sccm.

The above process parameters provide a typical deposition rate for thelow-dielectric constant amorphous carbon layer in the range of about 500Å/min or more, such as between about 1,500 Å/min to about 2,500 Å/min,and can be implemented on the same or different chemical vapordeposition chamber in a conventional parallel-plate radio-frequency (RF)plasma enhanced chemical vapor deposition (PECVD) system, available fromApplied Materials, Inc., Santa Clara, Calif., as the system fordepositing the silicon-containing inorganic barrier layer forconvenience. The amorphous carbon deposition values provided herein areillustrative and should not be construed as limiting the scope of theinvention.

The deposited low-dielectric constant amorphous carbon material includescarbon and hydrogen atoms, which may be an adjustable carbon:hydrogenratio that ranges from about 10% hydrogen to about 60% hydrogen.Controlling the hydrogen ratio of the amorphous carbon layer isdesirable for tuning its respective optical properties, etchselectivity, and chemical mechanical polishing resistance properties.Specifically, as the hydrogen content decreases, the optical propertiesof the as-deposited layer, for example, the index of refraction (n) andthe absorption coefficient (k), increase. Similarly, as the hydrogencontent decreases, the etch resistance of the amorphous carbon layerincreases. It is understood that embodiments of the invention includescaling up or scaling down any of the process parameter/variables asdescribed herein according to substrate sizes, chamber conditions, etc.,among others. It is also noted that embodiments of the invention do notrequire the steps to be performed in the order as described herein. Forexample, a hydrogen gas can be delivered into the process chamber beforea mixture of the precursors is delivered into the chamber, and in somecases, steps 704 and 706 can be performed at the same time. Optionally,a nitrogen-containing gas, such as a nitrogen gas, is supplied into agas mixture at a flow rate between about 200 sccm and about 5,000 sccm,such as between about 1,000 sccm and about 2,000 sccm.

EXAMPLES

FIG. 8 illustrates a flow chart of one exemplary deposition method 800in accordance with one embodiment of the invention. At step 802, one ormore silicon-containing inorganic barrier layers are deposited onto thesurface of a substrate in a substrate processing system using asilicon-containing compound and a hydrogen gas. At step 804, one or moreamorphous carbon layers are deposited in between the one or moresilicon-containing inorganic barrier layers in the same or differentsubstrate processing system using a carbon-containing compound and ahydrogen gas. Preferably, an initial layer of a silicon-containinginorganic barrier material, such as a silicon nitride layer is depositedfirst to provide as a good water and oxygen barrier for any layersunderneath the silicon nitride layer and on the substrate.

FIG. 9 shows the optical transmittance of one exemplary barrier layerand exemplary low-dielectric constant material layer. The exemplarybarrier layer is a silicon nitride layer deposited by a mixture ofsilane, ammonia, nitrogen gas, and hydrogen gas, delivered at about 150sccm, about 400 sccm, about 1,500 sccm, and about 4,000 sccm,respectively, into a PECVD process chamber. The substrate was placedinto the PECVD process chamber at a spacing of about 900 mils and apressure of about 2.1 Torr was maintained. A plasma was applied from aRF power density of about 0.45 watts/cm² for a deposition time period ofabout 390 seconds in the presence of a substrate bias. A substratetemperature of about 70° C. is maintained during deposition, resultingin a deposition rate of about 1,700/min.

The exemplary low-dielectric constant material layer is an amorphouscarbon layer deposited by a mixture of acetylene, nitrogen gas, andhydrogen gas, delivered at about 200 sccm, about 1,000 sccm, and about500 sccm, respectively, into the same PECVD process chamber. Thesubstrate was placed into the PECVD process chamber at a spacing ofabout 900 mils and a pressure of about 1.5 Torr was maintained. A plasmawas applied from a RF power density of about 0.25 watts/cm² for adeposition time period of about 500 seconds in the presence of asubstrate bias. A substrate temperature of about 70° C. is maintainedduring deposition, resulting in a deposition rate of about 1,200angstroms/min.

The light transmittance measurement of the deposited silicon nitridefilm (910) and the deposited amorphous carbon film (920) are shown inFIG. 9. The transmittance for both films at different wavelengths isvery high, on the average of between about 65% to about 100%. At highwavelengths of about 500 nm or larger, the transmittance is even better,having between about 90% to about 100% light transmittance. The resultssuggest that the silicon nitride and amorphous carbon films of theinvention can also be used in a variety of applications, including topor bottom emissive display devices.

Referring back to FIG. 8, at step 806, a silicon-containing inorganicbarrier layer is optionally deposited as the final layer. Thus, anencapsulating layer having the one or more silicon-containing inorganicbarrier layers and the one or more amorphous carbon layers is depositedon the surface of the substrate at step 808. Accordingly, variousencapsulating films having one layer, two layers, three layers, fourlayers, or five layers of a barrier material can be deposited.Similarly, various encapsulating films having one layer, two layers,three layers, four layers, or five layers of a low-dielectric constantmaterial can be deposited.

For example, various encapsulating films having one layer, two layers,three layers, four layers, or five layers of amorphous carbon materialin between two layers, three layers, four layers, five layers or sixlayers, respectively, of silicon nitride material were deposited andcompared/tested. In addition, the silicon-containing inorganic barrierlayers and the amorphous carbon layers deposited at various thickness orin the presence and absence of a hydrogen source gas were also tested.

The encapsulating films of the invention, having the silicon-containinginorganic barrier layers and the amorphous carbon layers, were testedusing a scotch tape peeling test and a calcium test. The results werevery good, showing no peeling of the various multilayer encapsulatingfilms from the substrate and no or low level of water and oxygencorrosion (no or low level of transparent calcium salt formation in acalcium test). The encapsulating films of the invention were also testedon devices, such as OLED devices, for their ability to be deposited to adesired thickness without peeling off the surface of the devices andprevent water and oxygen being penetrated into the devices andlengthening the device lifetime. When tested under about 60° C. and athigh humidity of about 85%, the encapsulating films of the invention canlengthen the lifetime of the devices to be more than about 1440 hours.

One exemplary multilayer encapsulating film deposited using methods ofthe invention is shown in FIG. 10, a cross sectional scanning electronmicroscopy micrograph of a substrate 1010 with a multilayerencapsulating film 1020 deposited on top. The multilayer encapsulatingfilm 1020 of the invention include four layers of a silicon nitridebarrier material 1011, 1012, 1013, 1014 and three layers of an amorphouscarbon material 1021, 1022, 1023 in between the silicon nitride materialto promote the adhesion of silicon nitride material, making a finalthickness of the multilayer encapsulating film 1020 to be about 35,000angstroms. The overall step coverage of the multilayer encapsulatingfilm 1020 with a total of nine deposited material layers is very good,about 95% step coverage obtained.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An encapsulating film formation method, comprising: depositingalternating layers of one or more barrier layers and one or morelow-dielectric constant layers, the one or more barrier layers depositedby delivering a first mixture of precursors and hydrogen gas, a firstlayer of the alternating layers comprises one layer of the one or morebarrier layers, and a last layer of the alternating layers comprisesanother layer of the one or more barrier layers.
 2. The method of claim1, wherein the first mixture of precursors comprises a compound selectedfrom the group consisting of silane, SiF₄, Si₂H₆, and combinationsthereof.
 3. The method of claim 2, wherein the first mixture ofprecursors further comprises a nitrogen-containing compound selectedfrom the group consisting of ammonia (NH₃), nitrous oxide (N₂O), nitricoxide (NO), nitrogen gas (N₂) and combinations thereof.
 4. The method ofclaim 2, wherein the first mixture of precursors further comprises acompound selected from the group consisting of a carbon-containing gas,an oxygen-containing gas, and combinations thereof.
 5. The method ofclaim 1, wherein the one or more barrier layers comprise a materialselected from the group consisting of silicon nitride, siliconoxynitride, silicon oxide, silicon carbide, and combinations thereof. 6.The method of claim 1, wherein the one or more low-dielectric constantmaterial layers comprise a material selected from the group consistingof amorphous carbon, diamond-like carbon, and combinations thereof. 7.An encapsulating film formation method performed within a substrateprocessing system, comprising: depositing one or more inorganic barrierlayers onto a surface of a substrate by delivering a first mixture ofprecursors and hydrogen gas into the substrate processing system; anddepositing one or more low-dielectric constant material layersalternating with the one or more inorganic barrier layers by deliveringa second mixture of precursors into the substrate processing system. 8.The method of claim 7, wherein the first mixture of precursors comprisesa compound selected from the group consisting of silane, SiF₄, Si₂H₆,and combinations thereof.
 9. The method of claim 8, wherein the firstmixture of precursors further comprises a nitrogen-containing compoundselected from the group consisting of ammonia (NH₃), nitrous oxide(N₂O), nitric oxide (NO), nitrogen gas (N₂) and combinations thereof.10. The method of claim 8, wherein the first mixture of precursorsfurther comprises a compound selected from the group consisting of acarbon-containing gas, an oxygen-containing gas, and combinationsthereof.
 11. The method of claim 7, wherein the one or more barrierlayers comprise a material selected from the group consisting of siliconnitride, silicon oxynitride, silicon oxide, silicon carbide, andcombinations thereof.
 12. The method of claim 7, wherein the one or morelow-dielectric constant material layers comprise a material selectedfrom the group consisting of amorphous carbon, diamond-like carbon, andcombinations thereof.
 13. The method of claim 7, wherein the secondmixture of precursors comprises a compound selected from the groupconsisting of acetylene (C₂H₂), ethane (C₂H₆), ethene (C₂H₄), methane(CH₄), propylene (C₃H₆), propyne (C₃H₄), propane (C₃H₈), butane (C₄H₁₀),butylene (C₄H₈), butadiene (C₄H₆), benzene (C₆H₆), toluene (C₇H₈), andcombinations thereof.
 14. An encapsulating film formation methodperformed within a substrate processing system, comprising: depositingone or more barrier layers onto a surface of a substrate by delivering afirst mixture of precursors and hydrogen gas into the substrateprocessing system; and depositing one or more low-dielectric constantmaterial layers alternating with the one or more barrier layers bydelivering a second mixture of precursors and hydrogen gas into thesubstrate processing system.
 15. The method of claim 14, wherein thefirst mixture of precursors comprises a compound selected from the groupconsisting of silane, SiF₄, Si₂H₆, and combinations thereof.
 16. Themethod of claim 15, wherein the first mixture of precursors furthercomprises a nitrogen-containing compound selected from the groupconsisting of ammonia (NH₃), nitrous oxide (N₂O), nitric oxide (NO),nitrogen gas (N₂) and combinations thereof.
 17. The method of claim 15,wherein the first mixture of precursors further comprises a compoundselected from the group consisting of a carbon-containing gas, anoxygen-containing gas, and combinations thereof.
 18. The method of claim14, wherein the one or more barrier layers comprise a material selectedfrom the group consisting of silicon nitride, silicon oxynitride,silicon oxide, silicon carbide, and combinations thereof.
 19. The methodof claim 14, wherein the one or more low-dielectric constant materiallayers comprise a material selected from the group consisting ofamorphous carbon, diamond-like carbon, and combinations thereof.
 20. Themethod of claim 14, wherein the second mixture of precursors comprises acompound selected from the group consisting of acetylene (C₂H₂), ethane(C₂H₆), ethene (C₂H₄), methane (CH₄), propylene (C₃H₆), propyne (C₃H₄),propane (C₃H₈), butane (C₄H₁₀), butylene (C₄H₈), butadiene (C₄H₆),benzene (C₆H₆), toluene (C₇H₈), and combinations thereof.